Factors Associated with Early versus Delayed Expansion of Acute Subdural Hematomas Initially Managed Conservatively

Acute subdural hematomas (ASDHs) are highly morbid and increasingly common. Hematoma expansion is a potentially fatal complication, and few studies have examined whether factors associated with hematoma expansion vary over time. To answer this, we performed a case-control study in a cohort of initially conservatively managed patients with ASDH. Two time periods were considered, early (<72 h from injury) and delayed (>72 h from injury). Cases were defined as patients who developed ASDH expansion in the appropriate period; controls were patients who had stable imaging. Associated factors were determined with logistic regression. We identified 68 cases and 237 controls in the early follow-up cohort. Early ASDH expansion was associated with coagulopathy (adjusted odds ratio [aOR] 2.3, 95 % CI: 1.2-4.5; p = 0.02), thicker ASDHs (aOR 1.1, 95% CI: 1.03-1.2; p = 0.006), additional intracranial lesions (aOR 3, 95% CI: 1.6-6.2; p = 0.002), no/minimal trauma history (aOR 0.4, 95% CI: 0.2-0.9; p = 0.03), and duration between injury and initial scan (aOR 0.9, 95% CI: 0.8-0.97; p = 0.04). In the delayed follow-up cohort, there were 41 cases and 126 controls. Delayed ASDH expansion was associated with older age (aOR 1.3 per 10 years, 95% CI: 1.1-1.6; p = 0.01), systolic blood pressure (SBP) >160 on hospital presentation (aOR 4.5, 95% CI: 1.8-11.3; p = 0.001), midline shift (aOR 1.5 per 1 mm, 95% CI: 1.3-1.9; p < 0.001), and convexity location (aOR 14.1, 95% CI: 2.6-265; p = 0.013). We conclude that early and delayed ASDH expansion are different processes with different associated factors, and that elevated SBP may be a modifiable risk factor of delayed expansion.